All-fiber add-drop filters based on microfiber knot resonators

Area of Science:

• Photonics
• Optical Engineering
• Materials Science

Background:

• Fiber optic components are crucial for telecommunications and sensing.
• Developing compact and efficient optical filters is an ongoing challenge.
• Microfiber knot resonators offer unique properties for optical applications.

Purpose of the Study:

• To demonstrate a novel all-fiber add-drop filter.
• To investigate the performance of microfiber knot resonators in an add-drop configuration.
• To assess the impact of coupling geometry on filter characteristics.

Main Methods:

• Fabrication of a microfiber knot resonator.
• Integration of the resonator with a fiber taper for dropping.
• Experimental characterization of the add-drop filter performance.
• Varying the microfiber knot diameter and coupling configuration (parallel and perpendicular).

Main Results:

• Achieved a quality factor (Q factor) of 13,000 with a parallel-coupling 308 micrometer diameter microknot.
• Obtained a Q factor of approximately 3300 with a cross-coupling 65 micrometer diameter microknot.
• Measured a free spectral range (FSR) of 1.8 nm for the parallel-coupling filter and 8.1 nm for the cross-coupling filter.
• Demonstrated ease of fabrication and integration with existing fiber systems.

Conclusions:

• The microfiber knot add-drop filter is a promising device for optical filtering.
• The device offers a simple and effective solution for add-drop multiplexing.
• The design allows for tunable performance based on geometry and coupling.
• Potential applications in optical communication networks and integrated photonics.